I am trying to develop a coating system consisting of epoxy bisphenol A (DGEBA) as a resin and hydroxyl-terminated poly dimethyl siloxane (HPDMS) as a modifier that will use for anti-corrosion purpose.
I presume that you use relatively low molecular weight versions of both epoxy and and silicone. I do not know, what kind of corsslinker you use. If all components are liquid, you can first try to achieve a homogeneous mixture before crosslinking. Even so it may happaen that you will observe phase seaparation during crosslinking. You may find useful studying the Tegomer (Evonik products). They offer a wide range of functionalized siloxanes with epoxy, OH, aminet etc. end groups and silicone-hydrocarbon waxes. This provides a selection to experiment with.
I have made coatings similar to what you describe and there are several ways that are functionally the same.
In a 2K coating, it is best to simply blend the silicone and epoxy resins in Part A. In Part B use a difunctional crosslinker, such as aminopropyl trimethoxysilane. See US patent US20130029311 for a robust example.
An alternative method is to use an epoxysilane monomer in the epoxy resin synthesis. This works well for moisture cured epoxy coatings and it is simple to evaluate the formula cost/performance ratio.
A third option is to simply post-add some supplier silane resin to an epoxide coating. There are many product examples and solvent combinations.